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T P Curtis

Publications and source records attributed to T P Curtis.

12 recordsLinked to original sources
PubMed2006

Towards the design of diversity: stochastic models for community assembly in wastewater treatment plants.

We believe that the engineering of wastewater treatment systems would be improved if we could predict and manipulate the composition, that is, the diversity of such systems. This ability would complement our established ability to predict the size of treatment communities. The theoretically based design of diversity in wastewater treatment systems is held by some to be unnecessary and by others to be impossible. In this paper we point to important phenomena in wastewater treatment, such as acclimation, adaptation and functional redundancy that would benefit from the ability to confidently design diversity. We set out a rationale and a mathematical framework for a stochastic approach to the design of diversity and show that, in principle, this approach works with two important functional groups in wastewater treatment. The implications for design and theory are briefly discussed.

Bacteria↗
PubMed2003

Variable photosynthetic characteristics in waste stabilisation ponds.

Algae play several key roles in waste stabilisation ponds. A model has been developed to predict algal concentration in waste stabilisation ponds, in which the relationship between photosynthesis and underwater light availability is central. One equation was selected from several alternative expressions that describe this relationship. The selected equation consisted of four photosynthetic parameters. A field sampling programme was designed to investigate the relationships between the photosynthetic parameters and the pond environment. Although initial regression analyses were unsuccessful, distinct diurnal variations were revealed in two key photosynthetic parameters, related to an inverse variation in chlorophyll a concentration. This led to the derivation of a dynamic feedback hypothesis which challenges the classic assumption in algal modelling of constant photosynthetic parameters.

Bioreactors↗
PubMed2003

A comparitive study of ammonia-oxidizing bacteria in lab-scale industrial wastewater treatment reactors.

The diversity and community structure of the beta-proteobacterial ammonia oxidising bacteria (AOB) in a range of different lab-scale industrial wastewater treatment reactors were compared. Three of the reactors treat waste from mixed domestic and industrial sources whereas the other reactor treats waste solely of industrial origin. PCR with AOB selective primers was combined with denaturing gradient ge electrophoresis to allow comparative analysis of the dominant AOB populations and the phylogenetic affiliation of the dominant AOB was determined by cloning and sequencing or direct sequencing of bands excised from DGGE gels. Different AOB were found within and between different reactors. All AOB sequences identified were grouped within the genus Nitrosomonas. Within the lab-scale reactors there appeared to be selection for a low diversity of AOB and predominance of a single AOB population. Furthermore, the industrial input in both effluents apparently selected for salt tolerant AOB, most closely related to Nitrosococcus mobilis and Nitrosomonas halophila.

Ammonia↗
PubMed2002

Fate of Cryptosporidium oocysts in an immobilised titanium dioxide reactor with electric field enhancement.

We have undertaken simple proof of principle experiments to find out if electric field enhanced photo-oxidation using immobilised titanium dioxide will damage Cryptosporidium oocysts. Using a simple Petri dish reactor and two forms of immobilised titanium catalyst (sol-gel and thermal-film) we have tested the ability of this technology to affect Cryptosporidium oocysts permeability assessed by propidium iodide exclusion. Test and control reactor runs were significantly different (P = 0.007). The thermal-film reactor had the greatest effect (approximately 27% of the seed) and was statistically distinguishable from the sol-gel reactor and the controls. The sol-gel reactor showed an increase in oocyst permeability, but was not statistically distinguishable from one of the controls. The enhanced performance of the thermal film reactor is attributed to the superior conversion of photochemical holes to hydroxyl radicals at the surface of this catalyst.

Animals↗
PubMed2002

In situ characterization of nitrifiers in an activated sludge plant: detection of Nitrobacter Spp.

AIMS: The purpose of this work was to investigate microbial ecology of nitrifiers at the genus level in a typical full-scale activated sludge plant. METHODS AND RESULTS: Grab samples of mixed liquor were collected from a plug-flow reactor receiving domestic wastewater. Fluorescent in situ hybridization technique (FISH) was used to characterize both ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) in combination with Confocal Scanning Laser Microscope (CSLM). Fluorescently labelled, 16S rRNA-targeted oligonucleotide probes were used in this study. Both Nitrosomonas and Nitrosospira genera as AOB and Nitrobacter and Nitrospira genera as NOB were sought with genus specific probes Nsm156, Nsv443 and NIT3 and NSR1156, respectively. CONCLUSIONS: It was shown that Nitrosospira genus was dominant in the activated sludge system studied, although Nitrosomonas is usually assumed to be the dominant genus. At the same time, Nitrobacter genus was detected in activated sludge samples. SIGNIFICANCE AND IMPACT OF THE STUDY: Previous studies based on laboratory scale pilot plants employing synthetic wastewater suggested that only Nitrospira are found in wastewater treatment plants. We have shown that Nitrobacter genus might also be present. We think that these kinds of studies may not give a valid indication of the microbial diversity of the real full-scale plants fed with domestic wastewater.

Ammonia↗
PubMed2002

A comparison of autotrophic ammonia-oxidizing bacteria in full- and laboratory-scale wastewater treatment reactors.

Lab-scale reactors are commonly used to simulate full-scale plants as they permit the effects of defined experimental perturbations to be evaluated. Ideally, lab- and full-scale reactors should possess similar microbial populations. To determine this we compared the diversity of the beta-proteobacterial autotrophic ammonia-oxidising bacteria (AOB) in a full-scale and lab-scale biological aerated filter (BAF) using PCR with AOB selective primers combined with denaturing gradient gel electrophoresis (DGGE). PCR amplified 16S rRNA gene fragments from the nitrification unit of the lab-and full-scale BAF were subjected to cloning and sequencing to determine the phylogenetic affiliation of the AOB. A high degree of comparability between the lab-and full-scale BAF was observed with respect to AOB populations. However minor differences were apparent. The importance of these minor constituents in the overall performance of the reactor is unknown. Nonetheless the lab-scale reactor in this study did appear to reflect the dominant AOB community within the full-scale equivalent.

Ammonia↗
PubMed2002

Are filamentous mycolata important in foaming?

In a previous study, we showed that there was a significant increase in mycolata numbers associated with foaming events at a wastewater treatment site possessing three activated sludge plants. In this paper, we demonstrate that branched filamentous mycolata were a minor proportion of the mycolata morphotypes present in those activated sludge plants, accounting for less than 21% of the mycolata population in the mixed liquor and foam samples examined. In most samples examined, the number of filamentous mycolata was negligible compared to the number of other mycolata morphotypes present. Furthermore, filamentous mycolata did not contribute to any of the significant differences in mycolata concentration observed between foaming and non-foaming situations (P<0.01). These findings suggest that conventional microscopic examination for monitoring mycolata populations in foaming plants may be misleading and should be used with caution.

Actinobacteria↗
PubMed2002

The effect of C/N ratio on ammonia oxidising bacteria community structure in a laboratory nitrification-denitrification reactor.

A laboratory scale reactor operated as a single sludge, denitrification-nitrification bioreactor (DNB), was fed a synthetic wastewater. The effect of the C/N ratio of the influent on the structure of beta-proteobacterial autotrophic ammonia-oxidizing bacterial (AOB) communities was determined by DGGE analysis of 16S rRNA gene fragments amplified using a range of AOB-selective primers. Fluorescence in situ hybridisation (FISH) was used to determine quantitative changes in the AOB communities. When operated at a C/N ratio of 2 the DNB was effective in nitrogen removal and nitrification was measured at approximately 1.0 mg NH4+-N/g dry wt/h. Altering the C/N ratio to 5 resulted in a 50% reduction in nitrification rates. Nitrification was restored to its original level when the C/N ratio was returned to 2. AOB were detected by DGGE analysis of samples from the DNB under all operating conditions but the changes in C/N ratio and nitrification rates were accompanied by changes in the community structure of the AOB. However, quantitative FISH analysis indicated that beta-proteobacterial AOB were only present in high numbers (ca. 10(8) cells/ml) under the original operating conditions with a C/N ratio of 2. Beta-proteobacterial AOB could not be detected by FISH when the C/N ratio was 5. When nitrification activity was restored by returning the C/N ratio to 2, beta-proteobacterial AOB were still not detected and it is likely that either beta-proteobacterial AOB were not responsible for ammonia oxidation or that beta-proteobacterial AOB that did not contain the target sites for the range of 4 AOB selective probes used, were present in the reactor.

Ammonia↗
PubMed2000

Quantitative use of fluorescent in situ hybridization to examine relationships between mycolic acid-containing actinomycetes and foaming in activated sludge plants.

The formation of viscous foams on aeration basins and secondary clarifiers of activated sludge plants is a common and widespread problem. Foam formation is often attributed to the presence of mycolic acid-containing actinomycetes (mycolata). In order to examine the relationship between the number of mycolata and foam, we developed a group-specific probe targeting the 16S rRNA of the mycolata, a protocol to permeabilize mycolata, and a statistically robust quantification method. Statistical analyses showed that a lipase-based permeabilization method was quantitatively superior to previously described methods (P << 0.05). When mixed liquor and foam samples were examined, most of the mycolata present were rods or cocci, although filamentous mycolata were also observed. A nested analysis of variance showed that virtually all of the measured variance occurred between fields of view and not between samples. On this basis we determined that as few as five fields of view could be used to give a statistically meaningful sample. Quantitative fluorescent in situ hybridization (FISH) was used to examine the relationship between foaming and the concentration of mycolata in a 20-m(3) completely mixed activated sludge plant. Foaming occurred when the number of mycolata exceeded a certain threshold value. Baffling of the plant affected foaming without affecting the number of mycolata. We tentatively estimated that the threshold foaming concentration of mycolata was about 2 x 10(6) cells ml(-1) or 4 x 10(12) cells m(-2). We concluded that quantitative use of FISH is feasible and that quantification is a prerequisite for rational investigation of foaming in activated sludge.

Actinomycetales↗
PubMed1992

Influence of pH, Oxygen, and Humic Substances on Ability of Sunlight To Damage Fecal Coliforms in Waste Stabilization Pond Water.

Simple beaker experiments established that light damages fecal coliforms in waste stabilization ponds by an oxygen-mediated exogenous photosensitization. Wavelengths of up to 700 nm were able to damage bacteria. The ability of wavelengths of >425 nm to damage fecal coliforms was dependent on the presence of dissolved sensitizers. The sensitizers were ubiquitous in raw sewage, unaffected by sewage treatment, not derivatives of bacteriochlorophyll or chlorophyll, absorbed well in UV light, and had a slight yellowish color; they are therefore believed to be humic substances. The ability of light to damage fecal coliforms was highly sensitive to, and completely dependent on, oxygen. Scavengers of H(2)O(2) and singlet oxygen could protect the bacteria from the effects of sunlight, but scavengers of hydroxyl radicals and superoxides could not. Light-mediated damage of fecal coliforms was highly sensitive to elevated pH values, which also enabled light with wavelengths of >425 nm (in the presence of the sensitizer) to damage the bacteria. We conclude that humic substances, pH, and dissolved oxygen are important variables in the process by which light damages microorganisms in this and other environments and that these variables should be considered in future research on, and models of, the effects of light.

Journal Article↗
PubMedDate not supplied

In situ detection of rhodococci associated with activated sludge foams.

Genus-specific 16S rRNA targeted oligonucleotide probes, Rco1 and Rco2, were designed and used to detect rhodococci in activated sludge foam samples by confocal laser scanning microscopy. Pure cultures were used to find the optimal hybridisation conditions which were determined by comparing the mean fluorescent intensities of target and non-target cells from images captured using a confocal laser scanning microscope (CLSM). The combination of fluorescent in situ hybridisation with rRNA-targeted oligonucleotide probes and confocal laser scanning microscopy provides an effective way of detecting rhodococci in environmental samples.

Bacteriological Techniques↗